Like the previous posters already stated:
The EST-version is for the Burton channel system, so don't buy that.
The Re:Flex technology is standard on the 2012 cartels, so if you buy the 2012 version, you don't have to worry about that. If you're buying an older version it is relevant, since the 2011 Cartels also had a non-re:flex version.
The Restricted version has a bigger (and asymmetrical) strap and most people think that's more comfortable. Restricted and non-restricted have the same price, but the restricted version is not sold everywhere so you'd have to search a bit for them.